Top screen for wood pulp digesters or the like



June 16, 1931. E. MORTERUD 1,810,845

TOP SCREEN FOR WQOD PULP DIGES'IERS OR TH E LIKE Filed larch 19. 1930 PatentedJune 1c, 1931 UNITED STATES may. MOBTERUD, F 'IOBDEBOD, NEAIB MOSS, HORST Ax TOP SCREEN I OB WOOD PULP DIGESTEBS OR THE m Application filed 1mm 19, 1930. se'ma'm. 437,093.

even if the normal screen or sieve openings be clogged, so as to be putout of operation.

This object is attained in accordance with the present invention by providing the screen or sieve surface with passages having a larger diameter than 'the ordinary holes of the screen, the intake to said passages being raised I a certain distance above the level of the screen, in order that they shall operate as overflow passages in case the ordinary openings of the screening surface become wholly or artly clogged,

ccording to a preferred embodiment of the invention the auxiliary overflow openings in accordance with the present invention are 2 v made in the form of short vertical tubes,

whichextend from the surface of the screen to a short distance above the same, the upper end' of said tubes being-preferably inclined,

so as to aflord a passage with gradually increasing capacity, as the level of digesting liquid on the screen rises.

- A preferred embodiment of the invention is diagrammatically illustrated on the drawing, which shows a vertical cross sectional view through the top of a wood pulp digester.

1 indicates the shell of the digester, 2 is the intake opening for filling the digester with wood fibers or the like, 3 'is the intake for 'gesting liquid, and 4 is a horizontal disuting screen for. distributing the di esting liquid over the cross sectional area 0 the di ster.

referably. the total cross sectional areaof the normal holes 5 creen 4 is sufl'icient to 5 permit the passage 0 the total amount of digesting liquid as soon as there is a slight head of liquid on the screen.

Should, however, part of the normal -open-. ings 5 be clogged for some reason, the liquid level on the screen will rise, and the surplus liquid will then flow over through the over; flow tubes 6, a number of which are distributed over the area of the screen, said overflow tubes having a considerably larger diameter than the ordinary screen holes, so that'they are not liable to be clogged by impurities.- The upper ends of said overflow tubes 6 are preferably out at an angle as indicated at so as to present a gradually increasing overflow area as the level of liquid rises. 00

Although the improvement in accordance with the present invention is particularly adapted for wood pulp digesters, it will easily be understood that it may also be utilized in connection with other similar vessels, which are provided at their top with horizontal screen 'or sieve surfaces for the distribution of liquid over the cross sectional area of the vessel.

'1. In 'a wood pulp digester or the like a screen or sieve near the top thereof for distributing liquid evenly-over the cross sec-. tional areaof the vessel, holes for the passage of liquid distributed over the area of '6 said sieve and auxiliary overflow passages having alarger individual cross sectional area than that of the said holes located a certain' distance above'the level ofithe sieve sur face. a

2. In awood pulp digester for the like a screen or sieve near the top thereof for distributing li uid evenly. over the cross sectional area 0 the vessel, holes for the passage of liquid distributed over the area of said 852 sieve and tubes passing through said screen or sieve and extending a certain distance above the level thereof so as to provide auxiliary passages for the liquid.

3. In a wood pulp digester orthe like a screen or sieve near the top thereof for distributing liquid evenly over the cross sectional area of the vessel, holes for the passage of liquid distributed over the area of said sieve and 'tubes: passing through saidscreen or sieve and extending a certain distance above the level thereof so as to provide auxiliary passages for the liquid, the ngper end of said tubes being inclined so as to a ord overflow passages with gradually increasing ca acity.

n testimony whereof I aflix my signature.

I EINAR MORTERUD. 

